drm/etnaviv: add cmdbuf suballocator

There are 3 big benefits to suballocating a single big DMA buffer
for command submission:

1. Avoid hammering CMA. The old way of allocating and freeing a DMA
   buffer for each submission was hitting some of the real slow
   pathes in CMA, as this allocator was not designed for a concurrent
   small buffers load.

2. Less TLB flushes on IOMMUv2. If a new command buffer is mapped into
   the GPU address space the MMU TLBs need to be flushed. By having
   one big buffer statically mapped to the GPU, a lot of those flushes
   can be avoided.

3. No funky workarounds for GC3000. The FE TLB flush on GC3000 isn't
   reliable. To work around that we tried to lay out the cmdbufs in
   the GPU address space in a way to avoid this issue. This hasn't
   always worked if the address space is crowded. A single statically
   mapped buffer avoids the erratum completely.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
index 3a689c3fbe5b..130d7d517a19 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
@@ -694,8 +694,15 @@ int etnaviv_gpu_init(struct etnaviv_gpu *gpu)
 		goto fail;
 	}
 
+	gpu->cmdbuf_suballoc = etnaviv_cmdbuf_suballoc_new(gpu);
+	if (IS_ERR(gpu->cmdbuf_suballoc)) {
+		dev_err(gpu->dev, "Failed to create cmdbuf suballocator\n");
+		ret = PTR_ERR(gpu->cmdbuf_suballoc);
+		goto fail;
+	}
+
 	/* Create buffer: */
-	gpu->buffer = etnaviv_cmdbuf_new(gpu, PAGE_SIZE, 0);
+	gpu->buffer = etnaviv_cmdbuf_new(gpu->cmdbuf_suballoc, PAGE_SIZE, 0);
 	if (!gpu->buffer) {
 		ret = -ENOMEM;
 		dev_err(gpu->dev, "could not create command buffer\n");
@@ -1598,6 +1605,11 @@ static void etnaviv_gpu_unbind(struct device *dev, struct device *master,
 		gpu->buffer = NULL;
 	}
 
+	if (gpu->cmdbuf_suballoc) {
+		etnaviv_cmdbuf_suballoc_destroy(gpu->cmdbuf_suballoc);
+		gpu->cmdbuf_suballoc = NULL;
+	}
+
 	if (gpu->mmu) {
 		etnaviv_iommu_destroy(gpu->mmu);
 		gpu->mmu = NULL;